I always wanted to to be a philanthropist and to give part of my body away to help others. Now at age 54, I am pleased to say I have done both.

I have had a successful real estate business. In 2003, I reached a point when I had provided for my kids and had access to liquid assets. So I gave away more than 50% of my assets to two dozens organizations in public health. I believe that if you have a charitable impulse you should act on it immediately. If you hold off and change your mind later that would be a crying shame. So many people could be cared for with small sums of money, especially in global public health. About 500,000 children a year become blind in poor countries for lack of small quantities of Vitamin A. Many children die from infections that Vitamin A would have prevented. One of the vehicles I set up with John Hopkins School of Public Health focuses on supplying that Vitamin A.

After giving away my money in 2004, I thought I would reward myself. Some people reward themselves with a candy bar when they have finished a study session. I treated myself to making a kidney donation. It was something I had always wanted to do.

I didn’t realize it was unusual to give a kidney, and even more so to donate one to a stranger. Still, giving a kidney seemed like a no-brainer to me. If you can save another person’s life without losing your own, why wouldn’t you do it?

I grew up in a very tiny house in Philadelphia. My father was a working man, a printer; my mother was a teacher. I still live relatively simply. I spent years teaching emotionally troubled inner city kids and also taught at the University of Pennsylvania where I earned doctorates in Rhetoric and Renaissance literature. Real estate investments I made at first in a small way eventually paid me a handsome return, and that made it possible for me to give millions away.

I live my life according to a simple moral principle: the greatest good for the greatest number of people, which I understand to mean that I should live on what I need and not more. As Gandhi said, “Live simply that others may simply live.”

But there are so many ways to give. A bus driver who always has smiles for his passengers is a philanthropist. Taking care of a sick relative for 20 years is philanthropy. You don’t have to give money or an organ. What you don’t need could be critical for others.